Rapidly quantifying the relative distention of a human bladder

ABSTRACT

A device and method rapidly quantifying the relative distention of the bladder of a human subject are disclosed. Ultrasonic transducer 1, which is positioned on subject 2 in proximity to bladder 16, is excited by pulser 3A under command of microprocessor 4 to launch an acoustic wave into patient 2. This wave interacts with bladder walls 12,13 and is reflected back to ultrasonic transducer 1, whence it is received, amplified, and processed by receiver 3B. The resulting signal is digitized by analog-to-digital converter 5 under command of microprocessor 4, and is stored in data memory 6B. The software in microprocessor 4 determines the relative distention of bladder 16 as a function of the propagated ultrasonic energy; and based on programmed scientific measurements and past history with the specific subject as contained in program memory 6A, sends out a signal to turn on any or all of the audible alarm 7, the visible alarm 8, the tactile alarm 9, and the remote wireless alarm 10.

ORIGIN OF THE INVENTION

The invention described herein was jointly made: in the performance ofwork under a U.S. Department of Education/National Institute forHandicapped Research grant to the Association for Retarded Citizens ofthe United States, and is subject to the provisions of the EducationDepartment General Administrative Regulations, revised July 1, 1985; andin the performance of work under a NASA Contract, and is subject to theprovisions of Section 305 of the National Aeronautics and Space Act of1958, Public Law 85-568 (72 Stat. 435; 42 USC 2457).

This is a continuation of application Ser. No. 07/118,993, filed Nov.10, 1987, and now U.S. Pat. No. 4,882,578, which application is acontinuation-in-part of co-pending application Ser. No. 06/929,869,filed Nov. 13, 1986 and now abandoned.

BACKGROUND OF THE INVENTION

This invention relates generally to the rapid signature analysischaracteristic of changes in an elastic membrane caused by stress, as afunction of energy transmitted into the membrane and reflectedtherefrom. It relates particularly to a device for rapidly quantifyingthe relative distention of the bladder of a human subject as a functionof ultrasonic energy transmitted into the subject and reflectedtherefrom.

There has been a long standing need for a device for rapidly quantifyingthe relative distention of bladders of human subjects, especially thementally retarded, the infirm, and the elderly.

In attempts to normalize the lives of persons with mental retardation,much energy has been devoted to teaching these persons how to functionindependently in society. The problem of incontinence often thwarts thebest of these efforts. While sophisticated toilet training programs arequite successful in teaching some persons what to do once the internalsensation of a full bladder is perceived, these programs typicallypresuppose that a person is capable of realizing when she/he has tovoid. The subset of the population of persons with mental retardationfor whom continued incontinence is a more common problem are thosepersons with severe or profound mental retardation, i.e., those with IQsless than 35 and significant deficits in adaptive behavior, who havedifficulty in recognizing the subtle and somewhat obscure signals oftheir bladders.

In addition, there is a substantial need to provide increasedindependence for persons who have permanently lost the ability tocontrol their bladders for medical reasons such as diabetes, cerebralpalsy, quadriplegia, spina bifida, and advanced age.

Incontinence typically results in a stigma for the person, reducedpositive interaction with other people, unsanitary living conditions,excessive laundry expenses, and increased custodial attention bycaregivers. Because of the failure to acquire fundamental toiletingskills, such persons are often excluded from a wide variety ofvocational, social, and recreational programs, in addition to manypreschool programs--all of which are important components of overallexperience necessary for their developmental growth and eventualintegration into community life.

Previous attempts to employ technology in urinary toilet training fallinto two classes. The first class is the wetness detector, which alertsthe subject when urine is present on the person. A particular example ofthis is the employment of a moisture-sensitive apparatus in the clothingor in the bed, which device triggers an alarm when moisture is detected.The second class is the motion-sensitive device, which is located in thetoilet. Once voiding has begun, the motion imparted to this device helpsthe user recognize that urination has been initiated. However, bothclasses of devices produce their effects after urination has takenplace. That is to say, their users are helped to recognize when voidinghas been initiated, but they are not helped to recognize the preliminaryneed to urinate, and thereby make the association between this need andsocially-acceptable toileting behavior. In neither case is there aquantification of the relative distention of the bladder, which would beof significance in helping one to recognize the preliminary need tourinate.

Urologists have recently employed an ultrasonic device which scans theentire bladder and images it with a sector scan to show the extent ofthe bladder wall over a sixty degree angle. Other recently-developeddevices are based on an ultrasonic "A" scan technique, using the time offlight of the sound wave between the front and back walls. These devicesare typically bulky and expensive. Moreover, even the most sophisticatedof the current devices suffers from inaccuracies resulting from theassumption of a simple, usually spherical, shape for the bladder. Inactuality, the bladder is not a sphere, rectangle, or other simplegeometric shape. It varies in shape continuously as it fills, varies inshape as between individuals, varies in height relative to the pelvicgirdle as between the sexes, and if it ever did approach the point ofbecoming a sphere, hyperdistention would be imminent.

While 50 cc of urine is considered to be a significant void volume, voidvolumes in test subjects varied from 30 cc up to over 600 cc. The testpopulation to date has tended to void between 180 and 400 cc. Thesubject perception is of increasing discomfort above approximately 200cc. In individuals with urinary disfunction the bladder has beeninflated through a catheter to upward of 600 cc with no real sensationbeing reported.

It is therefore a primary object of this invention to provide a devicefor the quantification of the relative distension of the urinary bladderof a human subject over a wide range of volumes, and with greateraccuracy than any non-scanning ultrasound device available from theprior art.

A further object of this invention is to provide adaptability to therequirements of a human subject in a user selectable manner, therebymimicking normal perception and affording help to the subject inrecognizing the appropriate time to urinate. Since an intendedapplication of the present invention is for individuals experiencingbladder disfunction for varying reasons and at varying ages, anadaptable operating system is a must. A microprocessor based design,with as much as possible of the functionality of the device in software,is indicated.

A further object of this invention is to provide a device for rapidlyquantifying the relative distention of the bladder of a human subject,thereby providing vital information needed by the subject during thecritical time when the bladder is at or near its full extention, andaffording help to the subject in recognizing the preliminary need tourinate.

Other objects and advantages of this invention will become apparent inthe specification and drawings which follow.

SUMMARY OF THE INVENTION

The present invention comprehends the provision of an ultrasonictransducer, which is positioned in proximity to the abdomen of thesubject under test, for the purpose of transmitting energy in the formof acoustic waves into the bladder of the subject followed by receivingacoustic waves reflected from the bladder of the subject. Apulser/receiver communicates with a source of power and the transducerand excites the transducer to transmit energy in the form of acousticwaves. It also amplifies and processes the reflected acoustic wavesreceived by the transducer and provides analog signals representative ofat least one reflected ultrasonic waveform over a respective timeinterval. A converter communicates with the pulser/receiver to digitizethe analog signal from the pulser/receiver to provide a correspondingdigital signal representative of at least one waveform. A memorycommunicates with the converter for storage of the digital signal fromthe converter. An input means provides a digital input signalrepresentative of a characteristic of the subject related to the amountof urine in the bladder. A logic system communicates with thepulser/receiver to command excitation of the ultrasonic transducer. Thelogic system communicates additionally with the converter to commanddigitization of the analog signals from the pulser/receiver. The logicsystem also communicates with the memory to receive the digital inputand the stored signals for processing the stored signals to provide afunction signal related to the value of the digitized signals and theirtime of occurrence within the respective time intervals, and forcomparing the function signal with stored, preselected function levelsto determine equivalency and to activate a preselected alarm upon theattainment of equivalency. The relative distention of the bladder of thehuman subject is thereby rapidly quantified.

According to the present invention, an ultrasonic transducer is placedin contact with the skin of the subject on the midline, just above thepubic symphisis. The transducer is coupled to the skin by means of amedically approved, water-based couplant. The transducer serves as bothpulser and receiving element in the pulse-echo system. An analog todigital converter processes the amplified echo return and supplies eightbit amplitude data, in a histogram format, to a controllingmicroprocessor. All control functions are contained in EPROM or areselectable from front panel BCD switches.

The genesis of this device was the need for an inconspicuously small,battery operated monitor that could be worn by an individual during thecourse of normal activities. The device should be adjustable by theindividual in areas such as setting the appropriate volume level for thealarm to be given, and the type, intensity, and duration of the alarm.Further, variations of the programming should be selectable, including asetup mode to assist in proper positioning of the transducer, as well asslightly different versions of the program to optimize the signalprocessing for individuals of different body sizes and configurations.

In the interests of mechanical, electrical and fiscal simplicity, an "A"scan format was chosen. The signal processing differs from the prior artas used in other "A" scan based instruments, which, even were they to bereduced to a comparable size, would suffer from inaccuracies in theinterpretation of the "A" line scan, related to the non-symmetric modeof expansion of a real bladder.

From Grey's Anatomy the depiction of the bladder shows an organ that iswell above the pelvic basin and with the major axis roughly parallel tothe abdominal surface in infancy. As the individual ages, the bladdersinks toward the pelvis. In the female, probably beginning at puberty,the bladder is typically lower than in the male. As the bladder slidesdown and back over time into the pelvis, the major axis becomes morehorizontal. In both the transverse and sagital sections the bladder isroughly triangular, until some degree of distention is arrived at. Theprogress of fill of the bladder is as follows: the cavity of the emptybladder takes the shape of a flattened "Y", with the urethra at thebottom. This is true in both the fore-aft plane and the lateral plane.The "Y" gradually fills to the top and then the actual expansion begins.The bladder expands in the fore-aft plane, and in the vertical plane,giving rationale for the front-wall to back-wall time of flightmeasurements. However, as will be delineated hereinafter, thenon-symmetric expansion of the bladder limits both the dynamic range andthe overall accuracy of a strictly time-based system.

In the information content of any ultrasound scan into the abdomen,there are a number of givens: the transmitted pulse and its associateddecay will be present, the transducer-skin interface will produce anecho, the skin to underlying muscle will produce an echo, and the muscleto abdominal cavity interface will produce an echo. These echoes willalways be present in the early portion of the return, on all subjects.At low levels of inflation, the front wall of the bladder is a poortarget. It is rounded point in the transverse section and even moreacute in the sagittal section. There is no single true diameter. Tocompound the problem, as the bladder expands, while it does become abetter target, the front wall also moves toward and eventually mergeswith the ever present abdominal wall eventually merges with the everpresent abdominal wall echoes at the front of the returning echo. All ofthis makes the front wall, for much of the range of bladder expansion, apoor marker. All of this does not negate the value of time of flightmeasurements, however, as the back wall will remain in view, and thetransducer itself can serve as the first marker.

The time of flight measurement, however, has an additionaldeficiency--lack of dynamic range. If the bladder were expanding in avacuum, this would not be the case. In the body, however, the bladdersoon runs out of room to expand to the rear, the sides and the front.Taking the path of least resistance, the primary direction of expansionin the upper ranges of volume is vertical, lifting and displacing theintestines. Movement in individuals who have had major abdominal surgerycan produce some interesting vectors.

An additional factor that has a bearing on the analysis of data derivedfrom an "A" line scan is that the movement of the back wall of thebladder, other than in very young children, is not a direct translation,but rather the elevation of the angle of a curved surface relative tothe axis of the insonating beam. Further, as this surface becomes moreperpendicular to the axis, it is also effacing the rugose foldscharacteristic of the lining of the empty bladder. The net effect ofthese actions is to make the back wall a better reflector as the bladderdistends.

There are two other mechanisms having an effect on the echo return athigher volume levels which have now come to light as a result of thepresent invention. At any acoustic interface, some portion of theincident wave will be reflected and some will pass through. This is trueof the back wall of the bladder, particularly at the higher levels ofdistention. The insonating beam passes through a greater distance of thelow attenuation urine than formerly, and the back wall has become abetter target. Some portion of the energy will penetrate the back walland produce reflections from the muscle layers surrounding the bladder.In addition, the distended bladder is now pressing against the organsand blood vessels that surround it.

Movements and pulsations in these organs are impressed on the wall ofthe bladder. The net effect of these two conditions is to cause anapparent increase in the duration of the back wall echo, which isrelated to increasing distention.

The difference between the present invention and previous "A" scantechnology is that the resident software algorithm keeps track of all ofthe variables, assigns weighted values to them, depending on theirrelative information content, and then derives a discrete numericalvalue for the perceived volume in each scan. That value is put intomemory and the trend of the value is periodically time averaged, withthat resultant both saved and made available for display.

By fully exploiting not just the location of the bladder wall, but alsothe information extractable from the changing signature of the wallechoes, the range of volumes through which the relative bladderdistention can be tracked is substantially enhanced.

As is understood by those of skill in the art from the foregoing, rapidquantification of the relative distention of the bladder of a humansubject is achieved according to the present invention by transmittingan acoustic wave into the bladder of the human subject so as to create areflected acoustic waveform; measuring a time range together with anenergy level of the reflected acoustic waveform; applying a signalprocessing algorithm thereto; and comparing the resulting measurementagainst a selectable standard.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, includingits objects and benefits, reference should be made to the detaileddescription, which is set forth below. This detailed description shouldbe read together with the accompanying drawings, wherein:

FIG. 1 is a functional block diagram of a preferred embodiment of thepresent invention;

FIGS. 2(a), (b), (c) is a three-part diagram showing in simplifiedgraphic form the acoustic beam path interaction with an empty bladder; arendering of the oscilloscope presentation of the amplified and detectedoutput resulting from that interaction: and the same waveform indigitized format, respectively;

FIGS. 3(a), (b), (c) is a three-part diagram in the same format as FIG.2, but with the bladder in a partially distended state;

FIGS. 4(a), (b), (c) is a three-part diagram in the same format as FIGS.2 and 3, but with the bladder in a well-distended state:

FIG. 5(a) is an amplitude histogram of a discrete digitized echowaveform;

FIG. 5(b) is a graphical illustration of a time/weighting curve appliedto the date in FIG. 5(a);

FIG. 5(c) is the resulting weighted histogram which will be processed byan algorithm to give a numerical equivalent; and

FIG. 6 shows the progression of a typical data trend line versus desiredvolume for alarm activation.

DETAILED DESCRIPTION OF THE INVENTION

The block diagram in FIG. 1 illustrates a preferred embodiment of thedevice according to the present invention. The system is under thecontrol of microprocessor 4, with all programming stored in a 64K EPROM6A,B. At turn on, read gate 14 is enabled and the status of the two BCDswitches 15A,B is determined. Switch 15A sets the desired volume levelat which an alarm is to be sounded. Switch 15B selects the operatingmode of the system and the display status. The microprocessor 4 thensends the first command to pulse. This pulse activates power amplifier3A which drives transducer element 1. The piezoelectric transducerelement produces a burst of 0.5 MHz sound waves when the 300nano-second, 12-volt DC pulse is applied to it. This is the transmitportion of the scan, which lasts for approximately 40-microsecondsincluding the pulse decay time. The system then goes into a listeningmode for approximately 250-microseconds. The receiver 3B consists of aninput differential amplifier; and absolute value detector, and an outputgain block. The output of the receiver is limited to a swing between 0and +5 volts. Any returning echo is amplified, conditioned, and appliedto the input of analog-to-digital converter 5. The converter is enabledby the same command to pulse as the power amplifier. Since the receiver"sees" the transmitted pulse as well as the echo, the first40-microseconds after T_(O) is ignored. This prevents the transmittedpulse from creating an error artifact. Starting after the end of thetransmit pulse, the A-D converter 5 performs 128 successivequantitizations, each occupying a time block of 1.7 microsecond. Thedepth into the abdomen of patient 2 insonated in this length of time hasproven, in all of the test cases to date, to be sufficient to view theback wall of bladder 16.

The echo return contains some amount of low level noise, which can beremoved by thresholding. Short term pulsations (usual durationapproximately 1/2 second) that appear to be caused by peristaltic actionin the intestines, are removed by time averaging. Because the amount ofintentinal overlay of the bladder and the resident ambient noise isquite variable between individuals--with children tending to givecleaner returns than adults--the number of scans to be averaged, theirspacing and the update rate can all be varied to suit the user. Betweenactive cycles, power control 18A is employed to maximize the life ofbattery 18B. In the current configuration (which was optimized for atest population of adult males) four individual pulse-echo scans aretaken and processed at eight millisecond intervals, the results areaveraged, the weighting algorithm is performed, and the results thereofplaced into data memory 6B. Four seconds later another group of fourscans is taken, processed, averaged and placed into data memory 6B. Thisprocedure is repeated four times. After the fourth iteration, theresults of the entire group are averaged, the output of display 17 isupdated, and the numerical value is compared to the value of the desiredalarm volume level. If the currently perceived volume value meets orexceeds the desired level, then the selected alarm is activated. Inorder to accommodate the varying needs of the individual users, both thetype and the duration of the alarm are switch selectable. The alarmsuite is comprised of visual 8, tactile 9, and audio 7 (volume is alsoadjustable), and remote 10. Alarm duration is adjustable from one secondto eight seconds in one second increments.

In actual practice, the setup and utilization of the device of thepresent invention is straightforward. The individual under test isallowed to accumulate some quantity of urine in the bladder by simplydrinking a fluid and waiting approximately thirty minutes. Thetransducer 1 with a suitable couplant is applied to the abdomen ofsubject 2 in the area just above the pubic hair. The transducer 1 isthen moved around to obtain a maximum reading on display 17 with thedevice set to pulse continuously. This is taken to be an indication thatbladder 16 is in the view of the insonating beam, as an empty bladder ora misaligned beam will afford very low numerical values. The (arbitrary)numerical range shown on display 17 has typically varied in the testpopulation from a value of 8-10 representing an essentially emptybladder--up to a reading of 55-65--representing volumes in excess of 500cc. Alarm level switch 15A permits the selection of sixteen levelsranging from 9-57. This is an arbitrary range based on the statistics ofthe test population who tended to void between values of twenty-four,which typically gave volumes of 240-260 cc, and forty-two, which gavevolumes of approximately 400 cc. The transducer 1 is secured to patient2 by an elastic belt, similar in construction to a hernia truss belt.The electronics package, including power control 18A and battery 18B, iscarried in a case on a shoulder strap.

In practice, with the device being worn by an individual for an extendedperiod of time who is going through the normal daily routines, someoperational characteristics were noted. When a normal, functioningindividual accumulates some volume in his/her bladder, the physiologicalsensation is not constant. When the feeling of need to urinate is firstapparent, it comes and goes, and the individual can be distracted. Asthe volume of urine increases, however, so does the frequency andurgency of the sensations, until such point as the individual feelssubstantial discomfort, which may be distracting from the task at hand,and he/she decides to void. Throughout, there are strains and posturesthat increase the physiological sensations. These are, however,transitory until the volume of urine becomes excessive.

The present invention mimics the type of progression set forth above.Since it is reasonable to assume that the individual will want toaccumulate an appreciable volume of urine in the bladder before takingthe time to void, an intermediate alarm level was selected for the testprogram. It was noted that when the bladder is empty, or when it has avery small amount of urine therein, body movement did not produce anyfalse alarms. When some amount of urine is present in the bladder,however, (80-100 cc) then body movement can produce an occasional,transitory alarm. When such movement ceases, the alarm stops. Of course,the individual could choose to void at this time, but, as is usually thecase with normal perception, the individual does not choose to void atthe first sensation. Rather, as time goes on and the alarm set level isapproached, the alarm (again as with the natural sensation) becomes moreand more frequent, until they are annoying. The individual, or theindividual's caretaker can over a period of time adjust the alarm levelto that point which works best for the individual involved.

To better understand the function and operation of the invention, it isnecessary to examine the acoustic wave interaction with the bladder asis shown in FIGS. 2-4. In FIGS. 2(a-c), the bladder is essentiallyempty. In FIGS. 3(a-c), the bladder is being filled, and in FIGS.4(a-c), the bladder is at maximum fullness. In each of FIGS. 2-4 aresimplified, illustrative diagrams of the physical bladder and theultrasonic transducer (A), a conventional ultrasonic signal S showingthe electrical radio frequency (RF) wave forms obtained from thetransducer after conversion in the receiver(B), and the energy waveforms E (C). Each of FIGS. 2-4 shows the tissue/transducer interface 11,the bladder front wall 12, and the bladder rear wall 13.

In FIG. 2, with the bladder essentially empty, transducer 1 is placed onthe patient with a conventional couplant for ultrasound. The sound waveexcited by the pulser/receiver 3 of FIG. 1 causes the ultrasonic signalshown in FIG. 2, diagram 2B, time position 11. The wave also reflectsoff the bladder front wall 12 and the bladder rear wall 13, with theresulting ultrasonic signals 12 and 13, respectively, in diagram 2B. Thebottom diagram 2C in FIG. 2 is the ultrasonic energy with itscorresponding signals 11, 12, and 13. These signals are obtained byadding the absolute amplitude of the RF wave forms for each pulse andaveraging the resulting summation over N cycles of the measurement, inaccord with the value weighting function by the programmed algorithm.

In FIG. 3, with the bladder partially full, the bladder has inflated asshown in diagram 3A of the figure, and the RF waveforms have changed asthe bladder shape has changed. In particular, the rear wall reflectionhas moved back in time, and additional reverberation has built up in therear wall signal as shown in 3B, wave 3 as well as in 3C, wave 3.

In FIG. 4, with the bladder substantially full, the change in shape hascontinued, although the rear wall 13 has not moved in a simple fashionduring filling. The energy seen in the rear wall reflection, however,continued to increase as the bladder was being filled. In fact, for abladder filling past about 60% fullness, the rear wall hardly moves atall, while the energy reverberation at the rear wall continues toincrease. Thus, it can be seen that a monitor of the rear wall positiononly would not be accurate during critical near-full periods. In sharpcontrast thereto, this invention, which measures the energy in the rearwall reflection as well as the rear wall position, is accurate as amonitor for the entire range of bladder fullness.

FIGS. 5 and 6 relate to the internal components of this invention andtheir function in more detail. The converter 5 and the memory 6 actuallyact as a signal averager, raking the digitizer output and multiplying itby some weighting function related to bin number, while checking thatthe signal falls in the correct time range or bin number (J). The entireoperation is controlled by the software to configure the function andthe mathematical operations for the specific subject.

As the simplist case, the function used is the sum of energy amplitudesin bins (J-K+W) that correspond to the rear wall and beyond of thebladder, where W is the width of the reverberation signal at the rearwall. A check on the data quality is that bins less than (J-K) show nosignificant amplitude. Such a lack of signal corresponds to the factthat when the bladder contains water, the path length between the frontand rear walls should show no scattering, i.e., a simple water pathexists.

The internal logic calculation of FIG. 6 shows the result of a typicalbladder during filling. The function has been adapted to the specificsubject so that the F(J,E) and the alarm threshold correspond to thebest time for that subject to be notified to urinate.

A complete electronics package is worn by the subject with thetransducer positioned by means of a flexible mounting belt. Theelectronics package advantageously contains means to alert the subjectwith any of a variety of stimuli including a tactile alarm (e.g., avibrator), a visual alarm (e.g., an LED mounted on eyeglasses), anaudible alarm (e.g., a buzzer), and a remote alarm (an RF link to areceiver monitor). In addition, the electronics package advantageouslycontains a working mode which lets the package work in a "sleep"configuration when the bladder should be empty (after successfulelimination). In that mode, the frequency of pulses and measurements isreduced to lengthen the life of the power supply (which isadvantageously a battery) in the package. Moreover, parameters governingthe user's interaction with the device, are entered by the user orhis/her caregiver into the logic system externally by adjusting controlson the face of the microprocessor. This affords a customization for eachindividual and a quick and simple modification of existing parameters atany time. The user or his/her caretaker is accordingly allowed to selectthe level of bladder fullness at which he/she would like the alarm tosound.

As is understood by those of skill in the art, the ultrasonictransducer, pulser/receiver, analog-to-digital converter, program anddata memory, audible alarm, visual alarm, tactile alarm, and remotealarm employed herein are per se well-known, and therefore are notdisclosed in detail herein.

The preferred embodiment of the invention disclosed hereinabove relatesto the propagation of ultrasonic energy and averaging the energy signalsover a number of measurement cycles to rapidly quantify the relativedistention of the bladder of a human subject. Moreover, the programmingof specific functions of the particular subject into the logic systempermits a fine tuning which affords accurate operation with a widevariety of subjects and conditions.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:
 1. A process for measuring the fullness of abladder in an animal body, comprising transmitting a pulse of energy toand through the bladder, receiving reflections of said pulse of energyover a selected period of time, identifying a set of segments of timeover said period of time, measuring the levels of the reflected energyreceived in each of said segments of time, and computing a measure ofbladder fullness from both the respective levels of energy in saidsegments of time and the location of said respective levels of energy insaid period of time.
 2. A process for measuring the fullness of abladder as set forth in claim 1, wherein the computing is done from saidrespective levels of energy primarily as reflected from a distal wall ofthe bladder and body tissue adjacent said distal wall.
 3. A process formeasuring the fullness of a bladder as set forth in claim 2, wherein theresults of said computing are compared with a preestablished reference.4. A process for measuring the fullness of a bladder as set forth inclaim 1, wherein a first of said reflections is from the proximate wallof said bladder, a second of said reflections is from the distal wall ofsaid bladder and adjacent body tissue, said second of said reflectionsextending over a plurality of said segments of time, and said computingof bladder fullness utilizes both the time between said first and secondof said reflections and the levels of energy in said segments of time ofsaid second of said reflections.
 5. A process for measuring the fullnessof a bladder as set forth in claim 1, wherein said pulse of energy is apulse of acoustic energy.
 6. A process for measuring the degree ofdistention of a distendable organ within an animal body, comprisingtransmitting a pulse of energy to and through the organ, receivingreflections of said pulse of energy over a selected period of time,identifying a set of segments of time over said period of time,measuring the levels of the reflected energy received in each of saidsegments of time, and computing a measure of the distention from boththe respective levels of energy in said segments of time and thelocation of said respective levels of energy in said period of time. 7.A process as set forth in claim 6, wherein the computing is done fromsaid respective levels of energy primarily as reflected from a distalwall of the organ body tissue adjacent said distal wall.
 8. A process asset forth in claim 6, wherein the results of said computing are comparedwith a preestablished reference.
 9. A process as set forth in claim 6,wherein a first of said reflections is from the proximate wall of saidorgan, a second of said reflections is from the distal wall of saidorgan and adjacent body tissue, said second of said reflectionsextending over a plurality of said segments of time, and said computingof organ distention utilizes both the time between said first and secondof said reflections and the levels of energy in said segments of time ofsaid second of said reflections.
 10. A process as set forth in claim 6,wherein said pulse of energy is a pulse of acoustic energy. 11.Apparatus for measuring the fullness of a bladder in an animal body,comprising means for transmitting a pulse of energy to and through thebladder, means for receiving reflections of said pulse of energy over aselected period of time, means for identifying a set of segments of timeover said period of time, means for measuring the levels of thereflected energy received in each of said segments of time, and meansfor computing a measure of bladder fullness from both the respectivelevels of energy in said segments of time and the location of saidrespective levels of energy in said period of time.
 12. Apparatus formeasuring the fullness of a bladder as set forth in claim 11, whereinthe computing is done from said respective levels of energy primarily asreflected from a distal wall of the bladder and body tissue adjacentsaid distal wall.
 13. Apparatus for measuring the fullness of a bladderas set forth in claim 12, and means for comparing the results of saidcomputing with a preestablished reference.
 14. Apparatus for measuringthe fullness of a bladder as set forth in claim 11, wherein a first ofsaid reflections is from the proximate wall of said bladder, a second ofsaid reflections is from the distal wall of said bladder and adjacentbody tissue, said second of said reflections extending over a pluralityof said segments of time, and the computing of bladder fullness utilizesboth the time between said first and second of said reflections and thelevels of energy in said segments of time of said second of saidreflections.
 15. Apparatus for measuring the fullness of a bladder asset forth in claim 11, wherein said pulse of energy is a pulse ofacoustic energy.
 16. Apparatus for measuring the degree of distention ofa distendable organ within an animal body, comprising means fortransmitting a pulse of energy to and through the organ, means forreceiving reflections of said pulse of energy over a selected period oftime, means for identifying a set of segments of time over said periodof time, means for measuring the levels of the reflected energy receivedin each of said segments of time, and means for computing a measure ofthe distention from both the respective levels of energy in said segmentof time and the location of said respective levels of energy in saidperiod of time.
 17. Apparatus as set forth in claim 16, wherein thecomputing is done from said respective levels of energy primarily asreflected from a distal wall of the organ and body tissue adjacent saiddistal wall.
 18. Apparatus as set forth in claim 16, and means forcomparing the results of said computing with a preestablished reference.19. Apparatus as set forth in claim 16, wherein a first of saidreflections is for the proximate wall of said organ, a second of saidreflections is from the distal wall of said organ and adjacent bodytissue, said second of said reflections extending over a plurality ofsaid segments of time, and the computing of organ distention utilizesboth the time between said first and second of said reflections and thelevels of energy in said segments of time of said second of saidreflections.
 20. Apparatus as set forth in claim 16, wherein said pulseof energy is a pulse of acoustic energy.